1. Field of the Invention
The present invention relates to an ultrasonic leakage inspection device of non-pressure type which performs leakage inspection of an item like a vessel, such as a fuel tank or a pipe.
2. Description of the Prior Art
For example, various types of closed vessels such as a fuel tank and a drum, are required to be inspected for leakage of a gas or a liquid from inside thereof. Pipes for buildings, facilities, and electric appliances are also required to be inspected for leakage of a gas or a liquid from inside thereof. The leakage inspection of these items has heretofore been carried out by various methods.
FIG. 1 shows a pipe 1 through which air or a gas flows under pressure and to which an inspection called a bubble type leakage inspection is applied. In the case that the leakage inspection of a connecting portion 3 between the pipe 1 and a joint 2 is done, a viscous liquid is sprayed like an arrow P while the joint 2 is rotated in the direction of an arrow Z, and the leakage is inspected on the basis of a forming condition of a bubble 4.
FIG. 2 shows a fuel tank 5 to which the same bubble type leakage inspection is applied. In the case that the leakage inspection of the fuel tank 5 is done, a lid 6 of an injection port is removed and air or a nitrogen gas is fed into the fuel tank 5 under pressure like an arrow Q through the injection port, and the lid 6 is then put thereon. Afterward, a viscous liquid is sprayed onto a portion to be inspected, such as a joint, and then the leakage is inspected on the basis of a condition of a bubble appearing on the portion.
In another inspection method which is called a water immersion type leakage inspection, air or nitrogen gas is injected into the inside of an item to be inspected, and the item is then hermetically sealed. Then, the item is immersed in water, and the leakage is then inspected on the basis of a condition of a bubble.
In a further inspection method which is called a helium type leakage inspection, the inside of an item to be inspected is evacuated, and the leakage inspection is then done by use of helium gas.
However, the above-mentioned conventional leakage inspection methods have the following problems.
The bubble type leakage inspection in which a viscous liquid is sprayed onto a portion to be inspected is laborious for the inspection, and after the inspection, a troublesome operation, such as wiping, is also required. In addition, such visual inspection is liable to miss defective portions of the items; and there is a problem that it is difficult to detect a very small leak. Moreover, in the case of the leakage inspection for piping, when portions to be inspected are complicatedly positioned among a plurality of pipes, there is a fear that it is impossible to do the spraying onto such complicated places. Additionally, when the portions to be inspected are concealed and so cannot be visually confirmed, there is a fear that the leakage inspection is impossible.
Besides, in the water immersion type leakage inspection in which air or nitrogen gas is fed under pressure into the item to be inspected, a troublesome working, such as drying, is required after the inspection, and so this type of inspection is laborious. Additionally, there is a problem that it is difficult to detect a very small leak.
Moreover, in the helium type leakage inspection in which the inside of the item to be inspected is evacuated and the leakage inspection is performed by use of helium gas, an inspection device is extremely expensive, and helium gas used for the inspection is also extremely expensive. In addition, a laborious and troublesome working must be performed.
The present invention has been made in consideration of the above-mentioned facts, and it is an object of the present invention to provide an innovative ultrasonic leakage inspection device of non-pressure type having a simplified structure which more easily detects the leakage of items, such as a vessel or a pipe.